the missile in problem 16 took 2 minutes to reach the height it attained. how much power was used?

Without the facts of problem 16, we have no way of knowing. Besides, how do we know the power was constant? It probably wasn't. Power increases with velocity, at constant thrust.

The average power (in watts) was
Pav = M*g*H/(120 seconds)

H is the height attained (in meters) and M is the mass (in kg), which might have been changing.